Solid state lasers have been found very useful for generating high power laser beams. A typical solid state laser has two main parts: a solid state laser medium and a pump source. The pump source can be another laser or array of lasers, an arc lamp, a flashlamp or some other suitable source of illumination. The solid state laser medium is typically a slab of material doped with appropriate active lasant, e.g., an active ion such as Nd, Er, Yb, Tm, Ho, etc.
Recently, slabs constructed to permit light to travel along a zig-zag path have gained popularity because of their ability to reduce thermal effects experienced by the slab during laser operation. Specifically, during high average power operation solid state lasers experience local refractive index variations, thermal lensing and stress birefringence of the slab. The geometry and further improvements to the zig-zag slab laser have addressed these problems and have helped to overcome the optical beam distortion due to these thermal effects. For more information about zig-zag slabs for solid state lasers the reader is referred to U.S. Pat. No. 4,894,839 to Baer; U.S. Pat. No. 5,479,430 to Shine, Jr., et al. and to U.S. Pat. No. 6,134,258 to Tulloch et al.
As slabs permitting zig-zag beam propagation have gained popularity, the technical challenge has shifted to fabrication methods. The doping of the slab can be achieved by a number of known approaches, including the Czochralski growth method, which is particularly well-suited for making slabs of YAG doped with Nd (Nd:YAG lasers). In order to achieve high power operation an optimal doping concentration balancing optical gain with optical loss is desirable. A method for achieving high active ion concentrations is described in U.S. Pat. No. 6,014,393 to Fulbert et al., as well as the other related applications. More specifically, Fulbert teaches how to achieve base material doping levels such that the ion concentration is equal to or higher than 2%. Further, recent research into lasers based on poly-crystalline host materials (i.e., ceramics) has led to Nd3+ dopant ion concentrations of around 10% in YAG.
The numerous advantages of zig-zag slab lasers are counterbalanced by the difficulties encountered in their manufacture. The prior art teaches several aspects of the manufacturing process of zig-zag slabs in U.S. Pat. Nos. 6,377,593; 6,472,242 and 6,566,152 all to Peterson et al.
The prior art also teaches which portion of the slab should be doped by Injeyan et al. in U.S. Pat. Nos. 6,094,297 and 6,256,142.
In addition, the prior art even teaches how to appropriately integrate elements into the slab—for example half/quarter wave plates—see the published patent application U.S. Patent Application 2002/0171918 to Clapp.
These prior art references teach how to build a zig-zag slab for use as laser or amplifier, however, the techniques disclosed are not suitable for batch processing. More particularly, they are not well-suited for rapid and low-cost manufacture of a large number of slabs for solid state lasers. This is especially true for cases where the performance and doping have to be well controlled and very good performance of the slab lasers is a requirement.